How to compress an image without wrecking its quality

Every "upload failed: file too large" error has the same boring solution: make the file smaller. The trick is doing it without turning your photo into porridge. Good news — there are only three knobs, and two of them are free of visible cost.

Knob 1: Dimensions before quality

A 6000×4000 photo displayed in a 1200px slot wastes 96% of its pixels. Shrinking the dimensions first is the single biggest win, and it's mathematically lossless as far as your visitors' eyes are concerned.

Rule of thumb: export at 2× the largest size the image will ever be displayed at. For most websites that's 1600–2400px on the long edge — not the 6000px your phone gave you.

Knob 2: The quality slider has a sweet spot

JPEG quality is not linear. Between 100 and 75 you lose almost nothing you can see, but you shed most of the file. Below 60 the artifacts start introducing themselves.

• 90–100: for print and portfolios — files stay chunky
• 75: the sweet spot — visually identical for web use, ~70% smaller
• 50–60: acceptable for thumbnails and avatars
• Below 50: only if you enjoy blocky skies

Knob 3: Pick the right format

Photos belong in JPEG or WebP. Screenshots and graphics with flat colors or text belong in PNG — or WebP if you want them smaller. WebP is the overachiever that does both, and every modern browser reads it.

The one mistake to avoid

Re-compressing a compressed file. Each pass throws away data the previous pass kept. Always compress from the original, and keep that original somewhere safe.